The dye molecule of this invention when applied to ordinary paper is highly waterfast against ordinary water and highly color-stable on basic paper. Since the dye is soluble in water having basic pH, an aqueous ink is achieved by formulas combining the dye and ammonia, as conventional for base-soluble dyes.
A number of dyes having similar, but not the same, structural formulas, are known and are found in the following list of references. However, no dye is known which provides the same excellent waterfastness and color fidelity as the dye of this invention when printed as a single ingredient on ordinary paper. The mechanism is not understood since similar molecules lack color fidelity significantly when applied to acid papers. The references are the following: U.S. Pat. No. 4,963,189 to Hindagolla; U.S. Pat. No. 4,841,037 to Ohta et al; U.S. Pat. No. 4,626,284 to Ohta et al; U.S. Pat. No. 4,594,410 to Pedrazzi; U.S. Pat. No. 4,143,035 to Stingl; U.S. Pat. No. 4,083,840 to Schoefberger; U.S. Pat. No. 2,265,425 to Fischer et al; U.S. Pat. No. 2,227,546 to Krebser; U.S. Pat. No. 2,112,920 to Mendoza; U.S. Pat. No. 1,913,382 to Gubelmann et al; U.S. Pat. No. 1,365,040 to Leaming; and U.S. Pat. 2,193,729 to Krebser; European Patent Application 356,080, application number 89308157.0, filed Aug. 10, 1989; German Patentschrift No. 725,224, dated Sep. 17, 1942; Great Britain No. 418,454; dated Nov. 22, 1934; Japanese patents/applications 1-313,568 dated Dec. 19, 1989; 64-79,277 dated Mar. 24, 1989; 60-243,176 dated Dec. 3, 1985; 60-243,157 dated Dec. 3, 1985; and Swiss Patentschrift 614,458 dated Nov. 30, 1979.
Rendering a base-soluble material soluble by including ammonium hydroxide in an aqueous ink is a conventional technique. Illustrative teachings are U.S. Pat. Nos. 3,891,581 to Argenio; Example XIII; found on column 13, of U.S. Pat. No. 5,017,644 to Fuller; and the foregoing U.S. Pat. No. 4,963,189 and European 356,080 (these two references have much identical content).